With the development of science and technology, the requirements for environmental humidity are becoming higher in many fields, for example, the environmental humidity should be effectively monitored in aerospace industry, agriculture, precision machinery and laboratory. At present, researching of humidity sensor is a hot direction of the researching of many sensor fields. The common humidity sensors are usually based on metal oxide materials. Although the stability of such humidity sensor is good, but the selectivity is poor and the preparation process is relatively complex, so that it is not suitable for large-scale application. In order to meet the requirements of the market for low cost, practical and easy preparation, a new type of humidity sensor is urgently needed.